1. Field of the Invention
The invention relates to an electron gun in cathode ray tube. More particularly, the invention relates to a focus electrode and an anode in an electron gun of a cathode ray tube (CRT).
2. Background of the Related Art
FIG. 1 illustrates a schematic side view section of a CRT. The CRT of FIG. 1 includes a panel 1 and a funnel 2 forming a front and rear of the CRT. An electron gun 3 is provided in a neck part 2a at one end of the funnel 2 for emitting electron beams 3a. A deflection yoke 4 is disposed around an outer surface of the funnel 2 for deflecting the electron beams 3a. A shadow mask 5 is positioned between the electron gun 3 and the panel 1 for passing the deflected electron beams 3a therethrough. A fluorescent surface 7 coated on an inside surface of the panel 1.
FIG. 2 illustrates a side view of the electron gun 3 built into the neck part 2a of the color CRT. Referring to FIG. 2, the electron gun 3 includes cathodes 8, a control electrode 9, acceleration electrode 10, first and second pre-focus electrode 11a and 11b, a focus electrode 12, and an anode 13, each having a preset voltage applied thereto. The control electrode 9 and the acceleration electrode 10 are planar. The pre-focus electrodes 11a and 11b, the focus electrode 12, and the anode 13 are non-circular cylindrical. Each have electron beam pass-through holes for passing electron beams 3a therethrough.
When the foregoing CRT is put into operation, the electron beams 3a are emitted from the cathodes 8, and accelerated toward the anode 13 by a potential difference. Since preset voltages are applied to respective electrodes, the electron beams are controlled, accelerated, and pre-focused, respectively, by the control electrode 9, the acceleration electrode 10, the pre-focus electrode 11a and 11b. The main focusing of the electron beams is performed by a main focus electrostatic lens formed by a potential difference between the focus electrode 12 and the anode 13. The electron beams 3a are, then, deflected in the up, down, left, and or right direction by the deflection yoke 4, selectively passed through the shadow mask 5, and land on the fluorescent surface 7 to form a picture on the panel 1.
In the case of electron guns in recent large-sized color CRTs where a heavy current is essential, the heavy current makes the electron beam flux thicker, and leads it to pass through a protaxis of the main focus electrostatic lens. The electron beam passing through the protaxis has more spherical aberration than one passing through a paraxis. The spherical aberration causes blooming, a phenomena in which a spot size of the electron beam is formed greater at a central part of the screen. It is known that a horizontal spot size caused by blooming can be reduced by a VM (velocity Modulation) coil fitted to an outer circumference of the neck. However, since there has been no proper device external to the CRT for reducing a spot enlarged in a vertical direction due to spherical aberration, vertical blooming still remains on the screen, and deteriorates a vertical focus characteristic of the screen.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
Accordingly, the invention is directed to an electron gun in a CRT that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the invention is to provide an electron gun in a CRT, in which a vertical diameter dv of a main focus electrostatic lens is configured to be greater in proportion to increased thickness of the electron beam flux where heavy current is used for the electron gun, preventing occurrence of spherical aberration, and improving a vertical resolution of a picture.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, an electron gun in a CRT includes three cathodes for emitting electron beams, a plurality of acceleration electrodes, and a focus electrode and an anode, each including an opposite rim having a single electron beam pass-through hole with a vertical width V and a horizontal width H, and an electrostatic field control body at a distance D from the rim, with a bridge width xe2x80x98txe2x80x99, and a vertical width v and a horizontal width h of a central electron beam pass-through hole, wherein the electrostatic field control body and the focus electrode and the anode can be related by the following equation (1):
(VxvxD)/29xe2x89xa7Hxe2x88x92(2xc3x97S),xe2x80x83xe2x80x83(1)
where, S denotes a sum of the horizontal width h and the bridge width t of the electrostatic field control body.
To further achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, an electron gun in a CRT includes at least one cathode for emitting electron beams, at least one acceleration electrode, and a focus electrode and an anode each including an opposite rim having an electron beam pass-through hole with a vertical width V and a horizontal width H, and an electrostatic field control body positioned at a distance D from the rim, with a bridge width xe2x80x98txe2x80x99, and a vertical width v and a horizontal width h of a central electron beam pass-through hole, wherein the electrostatic field control body and the focus electrode and the anode are configured to satisfy the following equation (1):
(VxvxD)/29xe2x89xa7Hxe2x88x92(2xc3x97S),xe2x80x83xe2x80x83(1)
where, S denotes a sum of the horizontal width h and the bridge width t of the electrostatic field control body.
To further achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, a method of optimizing the performance of an electrostatic field control body of an electron gun for a CRT includes (1) determining parameters influencing a vertical width dv of the electrostatic field control body, (2) determining parameters influencing a horizontal width dh of the electrostatic field control body; and (3) optimizing the electrostatic field control body based on the parameters determined in steps (1) and (2).
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.